1. Field of the Invention
The invention relates to a printer, and in particular to a matrix printer with a carriage guide running in parallel in front of a print-surface support for a print-head carriage, which supports a print head and where an ink-ribbon guide is disposed on the print-head carriage.
2. Brief Description of the Background of the Invention Including Prior Art
Such printers are operated by personnel which are in general not very skilled in technical matters and which have to exchange from time to time, in addition to the necessary replenishment of print-support materials, also worn and defective ink ribbons. Special printers, which are set during the operation to specific requirements, such as for example multiple-form printing or, respectively, savings-booklet printing, and the like, require today, in addition to the exchange of the ink-ribbon cassette, also an exchange of the print head. Such an exchange of the print head can become necessary based on various circumstances. On the one hand, defective print heads are to be exchanged against operable print heads and, on the other hand, other print heads should be exchanged amongst each other where they have different properties. For example, print heads can be equipped for standard-type printing and special print heads might be needed such as, for example, print heads which are suitable for optical character recording, OCR, writing. Therefore, if the operating personnel is required to exchange the print head for whatever reason, certain defined preconditions have to be adhered to. It is not possible to require the operating personnel to handle special tools and to perform certain extensive demounting operations, where loose parts are necessary for the attachment of the ink ribbon or, respectively, of the print head. It is not advantageous to use attachment parts, such as screws and nuts, since there exists the danger that these parts can be lost or can even fall into the interior of the printer and cause damage there. A further difficulty exists in that, during the exchange of the print head, the electric connection lines to the individual print elements on the print side have to be disengaged and they have to be reconnected after the insertion of another print head.
A carrier with a pin-print head is known from German Petit Patent DE-GM No. 7,800,250, where the print head is disengageably disposed on a special carrier and where the attachment is performed via a nose on the pin-guide casing, against which a bow is tensioned. This reference describes only the support and the attachment of the print head.
A different attachment for an exchangeable pin-print head is given in the German Petit Patent DE-GM No. 7,405,484 and requires a recess in the print-head carriage, where the recess has a partly circular and partly rectangular cross-section, into which recess the print head is inserted. In a certain way, the support is provided here by a bearing block. However, no solution is given in this reference relating to the electric connection part of the print head. Furthermore, the solutions taught do not provide any suggestions relating to the guiding of the ink ribbon.